Earth-boring tools for forming wellbores in subterranean formations may include cutting elements secured to a body. For example, a fixed cutter earth-boring rotary drill bit (“drag bit”) may include cutting elements fixedly attached to a bit body thereof. As another example, a roller cone earth-boring rotary drill bit may include cutting elements secured to cones mounted on bearing pins extending from legs of a bit body. Other examples of earth-boring tools utilizing cutting elements include, but are not limited to, core bits, bi-center bits, eccentric bits, hybrid bits (e.g., rolling components in combination with fixed cutting elements), reamers, and casing milling tools.
Cutting elements used in earth-boring tools often include a supporting substrate and cutting table, the cutting table comprises a volume of superabrasive material, such as a volume of polycrystalline diamond (“PCD”) material, on or over the supporting substrate. Surfaces of the cutting table act as cutting surfaces of the cutting element. During a drilling operation, cutting edges at least partially defined by peripheral portions of the cutting surfaces of the cutting elements are forced into contact with the formation. As the earth-boring tool moves (e.g., rotates) relative to the subterranean formation, the cutting elements are moved across surfaces of the subterranean formation and the cutting edges shear away formation material.
During a drilling operation, the cutting elements of an earth-boring tool may be subjected to high temperatures (e.g., due to friction between the cutting table and the subterranean formation being cut), high axial loads (e.g., due to the weight-on-bit (WOB)), and high impact forces (e.g., due to variations in WOB, formation irregularities, transitions between different formation materials, vibration, etc.). High temperature conditions can result in undesirable wear (e.g., formation of wear flats, dulling), while high axial loads and impact forces may result in damage (e.g., chipping, spalling) to the PCD material of the cutting tables of the cutting elements. The wear and/or damage often occurs at or near the cutting edges of the cutting tables, and can result in one or more of decreased cutting efficiency, separation of the cutting tables from the supporting substrates of the cutting elements, and separation of the cutting elements from the earth-boring tool to which they are secured.
For example, as mentioned above, wear flats may form from the cutting edges of the cutting tables rearwardly into sides of the cutting tables and ultimately into the sides of the supporting substrates. Such wear flats may be particularly undesirable where the cutting table is formed as a so-called “leached” polycrystalline diamond compact diamond table. A leached diamond table may be formed by leaching a catalyst material (e.g., cobalt) used to stimulate formation of the polycrystalline diamond compact from interstitial spaces between the inter inter-bonded diamond crystals in the diamond table using, for example, an acid or combination of acids (e.g., aqua regia). The catalyst material is generally removed from exterior portions of the diamond table to a depth from the cutting surfaces. For example, the catalyst material may be removed from the cutting face, from a portion of the side surface of the diamond table, or both, to a desired depth or depths within the diamond table, but without leaching all of the catalyst material out from an interior of the diamond table and a portion of the diamond table side surface adjacent to the supporting substrate. The leached portion of such a diamond table configuration results in enhanced thermal stability of the diamond table at and adjacent to the cutting edge, reducing the wear rate of the diamond and maintaining cutting efficiency, while the unleached portion provides structural strength against loading and impact. However, formation of wear flats may act to remove a majority or all of the leached portion of the diamond table, leaving mainly non-leached portions of the cutting table and resulting in decreased cutting efficiency, an increased wear rate and/or premature failure of the cutting table.
Accordingly, it would be desirable to have cutting elements with leached diamond tables, earth-boring tools (e.g., rotary drill bits) bearing such cutting elements, and methods of forming and using such cutting elements and earth-boring tools so equipped offering enhanced cutting efficiency and prolonged operational life during drilling operations as compared to conventional cutting elements with leached diamond tables, conventional earth-boring tools bearing such conventional cutting elements, and conventional methods of forming and using such conventional cutting elements and earth-boring tools so equipped.